Methods for finishing an aperture

ABSTRACT

A method of finishing a pre-formed aperture in a metal component, for example an extrusion tool opening, to achieve a desired surface finish for the side wall of the aperture, comprises the step of forcing an abrasive compound through the aperture in one direction only, i.e. the intended extrusion direction with an extrusion tool.

United States Patent 5l/28l P, 7, 8, 26, 290

Feldcamp 1 June 3, 1975 METHODS FOR FINISHING AN APERTURE [76] Inventor: Edward George Feldcamp, e0 References Cited Roberts Burns Ave., Benhall, UNITED STATES PATENTS Chats-ham, England 3,521,412 7/1970 McCarty 51 /317 22 Filed; 22 974 3,553,895 11/1967 Power 51/8 [21] Appl' 499780 Primary Examiner-Donald G. Kelly Related US, Application Dat Attorney, Agent, or Firm-Young & Thompson [60] Continuation of Ser. No. 299,247, Oct. 20, 1972, 1 abandoned, which is a division of Ser. No. 73,110, [57] ABSTRACT No? A method of finishing a pre-formed aperture in a metal component, for example an extrusion too] open- [30] Foreign Data ing, to achieve a desired surface finish for the side wall Sept. 17, 1969 United Kingdom 45940/69 of the aperture, comprises the Step of forcing an abm sive compound through the aperture in one direction [52] US. Cl 51/317; 5l/290 only the intended extrusion direction with an [51] Int. Cl B24b 1/00; B24b 5/40; B24b 5/48 trusion tool.

[58] Field of Search, 5l/317, 318,292,281 R,

3 Claims, 2 Drawing Figures METHODS FOR FINISHING AN APERTURE This is a continuation of application Ser. No. 299,247, filed Oct. 20, I972 now abandoned, which in turn isa divisional of application Ser. No. 73,1 10, filedSept.-l7, i970 now US. Pat. No. 3,699,725, issuedQct. 24,. 1972. N

This invention relates to a method for finishing a pre formed aperture or passage in acomponent to achieve a desired surface finish for the side wall of the aperture. It is of particular, but by no means exclusive, application to finishing the opening in an extrusion die or tool as used in the extrusion of aluminium sections. A further application is the de-burring of drilled passages in metal components.

At presentan extrusion tool is normally pre-formed using a spark erosion technique, and after heat treatment to provide the appropriate hardness for the extrusion tool the wall of the tool opening is finished by hand using small files and emery cloth to provide a satisfactory surface finish. This removes the etched" finish left by the spark erosion process, but it requires considerable skill and care if the shape of the opening is to be maintained and the die performance not affected due to an adverse slope being given to the various portions of the side wall. The performance of the finished tool depends upon a uniform speed of metal flow through the opening during extrusion, and the speed of flow at any point is largely determined by the inclination of adjacent portions of the side wall. Thus hand finishing is a skilled process and if badly done can easily result in a tool having to be scrapped, and hence it is essentially slow and expensive in terms of skilled labour.

The object of the invention is to provide a method and means which will replace the usual hand finishing of the opening in an extrusion tool, providing more uniform and accurate finishing while not requiring the employment of highly skilled labour.

To this end a method of finishing an opening in an extrusion tool, according to the invention, comprises mounting the tool in a holder, and forcing an abrasive compound through the tool in the intended extrusion direction. As it passes through the tool opening the compound abrades the side wall, and the abrasion process is continued until the desired finish is achieved.

The abrasive compound may be a liquid, a paste-like or a solid wax suspension of abrasive particles. For example the compound may Comprise particles of an abrasive such as silicon carbide in a base of so-called dental wax, i.e. the wax used to take dental impressions.

It will be appreciated that the abraded finish is uniform around the opening, so that the accuracy of the performed shape is not affected. The tool holder is desirably positioned at one end of a cylinder containing a ram which forces the abrasive compound through the tool in the intended extrusion direction and in a manner which simulates the extrusion process, i.e. openended extrusion is employed with the compound extruded into a free space in which it is not confined. Different grades of abrasive compound may be used to provide successive coarse and fine finishing.

Two embodiments of the invention in the form of means for finishing the opening of an extrusion tool, and the corresponding method of finishing, will now be described by way of example with reference to the accompanying drawings. in the drawings:

FIG. 1 is a part-sectional side view of one of the embodiments for use with a solid wax base abrasive compound, and

FIG. 2 is a similar view of means of the other embodiment foruse with a liquid base abrasive compound and showing diagrammatically means for recirculating the compound.

In each embodiment a cylinder 1 has a longitudinal and horizontal bore 2 within which a piston 3 is reciprocable on the end of a hydraulic ram 4. Thus reciprocation of the ram 4 forces the abrasive compound from the cylinder 1 through the tool opening 5, the tool 6 being held in a tool holder 7 during the finishing operation. The cylinder 1 is secured to a base plate 8.

In the embodiment of FIG. 1 the rear half of the cylinder is cut away above a horizontal diametral plane to provide a loading aperture, into which the abrasive wax compound is loaded with the piston 3 in the retracted position illustrated. The piston 3 is shown at the forward end of its stroke in broken lines, in which position the compound previously loaded has been forced through the tool opening in the intended extrusion direction and the piston is ready to commence a return stroke. The tool holder 7 is held in a tool carrier 9 with an end opening 10 through which the compound leaves the tool opening, and the carrier 9 is clamped against an end flange 12 of the cylinder by nuts 13 threaded on to tie rods 14 which pass through the flange 12.

A tool carrier 9 is slidably mounted on two parallel slide bars 15 so that on removal of the nuts 13 it can be moved away from the front end of the cylinder 1 to fit or remove the tool 6 and tool holder 7. A guide rod 16 is provided which projects rearwardly from an upper portion of the tool carrier 9 and is slidably guided through the cylinder flange 12. Movement of the carrier 9, when the nuts 13 are removed, is produced by a hydraulic ram 17.

A frame member 18 is welded to the base plate 8 and the cylinder flange 12, and a spaced frame member 19 supports the casing 20 of the ram 4. The ram 4 is, for example, capable of exerting a maximum force of the order of 50 tons, and this is withstood by the base plate 8 below the ram 4 and two angle section tie bars 22 extending between the upper edges of the front members 18 and 19.

In the embodiment of FIG. 2 the cylinder 1 is enlarged and counterbored at its front end at 23 to form a seating for the tool holder 7. The holder 7 is detachably retained in position by suitable means, for example radially displaceable pegs such as 24 which engage circumferential recesses 25 in the holder 7. The holder 7 has a through aperture 26 which is counterbored on its inner rear side to provide a sealing for the tool 6 during finishing.

The ram 4 is, for example, again capable of exerting a maximum pressure of 50 tons at a speed variable between one and ten strokes per minute. An inlet port 27 in the cylinder wall is uncovered when the ram 4 approaches the end of its return stroke. Two supply tanks 28 and 29 respectively contain coarse and fine abrasive compound in the form of a viscose liquid, and these tanks are respectively connected to the inlet port 27 through pipelines 30 and 31 each of which contains a shut off valve 32 or 33 and a pump 34 or 35. Thus either coarse or fine abrasive compound can be supplied to the cylinder 1 when the ram 4 is retracted, and during the next forward stroke of the ram 4 the compound is extruded through the tool opening 5 to finish the side wall of the latter by abrasion. Reciprocation of the ram is continued until the desired surface finish is obtained, the coarse compound being used initially and the final desired finish obtained using the fine compound.

After it has passed through the tool 6 the compound is collected within a hinged hood 36 and returned to the appropriate supply tank through a drain port 37 and two-way changeover valve 38. It is contained and caused to flow to a port 37 by the hood 36 which as shown normally shrouds the front end of the cylinder 1 but which can be lifted up for removal and replacement of the tool holder 7. Each of the tanks 28 and 29 has an internal high level filter 39 which cleans the compound and removes swarf, etc.

It is to be understood that references herein to a metal extrusion tool are to be read as referring to extrusion tools formed of metal and not necessarily to tools for the extrusion of metal.

I claim:

1. A method of finishing an opening in an extrusion tool having an intended extrusion direction, comprising mounting the tool in a holder and extruding an abrasive compound through the opening under pressure in the intended extrusion direction only and into a free space in which the compound is not closely confined, the compound being of solid extrudable nature such that it extrudes into the free space in a shape which simulates the extrusion which would result if the tool were put into service at that time.

2. A method of finishing according to claim I, wherein extrusion of the abrasive compound through the opening is effected by means of a piston reciprocable within a cylinder relative to which the holder is fixed and wherein loading of the abrasive compound into the cylinder is effected when the piston is withdrawn through a loading aperture formed in the cylinder.

3. A method of finishing according to claim 1, wherein the tool holder is mounted iri a carrier which is slidably mounted on slide bars and wherein movement of the carrier is effected by means of a hydraulic ram 

1. A method of finishing an opening in an extrusion tool having an intended extrusion direction, comprising mounting the tool in a holder and extruding an abrasive compound through the opening under pressure in the intended extrusion direction only and into a free space in which the compound is not closely confined, the compound being of solid extrudable nature such that it extrudes into the free space in a shape which simulates the extrusion which would result if the tool were put into service at that time.
 1. A method of finishing an opening in an extrusion tool having an intended extrusion direction, comprising mounting the tool in a holder and extruding an abrasive compound through the opening under pressure in the intended extrusion direction only and into a free space in which the compound is not closely confined, the compound being of solid extrudable nature such that it extrudes into the free space in a shape which simulates the extrusion which would result if the tool were put into service at that time.
 2. A method of finishing according to claim 1, wherein extrusion of the abrasive compound through the opening is effected by means of a piston reciprocable within a cylinder relative to which the holder is fixed and wherein loading of the abrasive compound into the cylinder is effected when the piston is withdrawn through a loading aperture formed in the cylinder. 